As others have mentioned. I have started buying whites and creams fabrics and good quality muslin for my backings. However I also then dye the fabric in colors that compliment the front. I use the ice cube method to dye them which gives them a marble or tie dye appearance that I really like. However I have just dyed the fabric a similar solid color as well (a quilt top with lots of blues I would probably dye the backing blue etc.)